Recently, researchers are paying attention to the use of the software development and code-hosting web service GitHub for other collaborative purposes, including a class of activity referred to as document, text, or prose collaboration. These alternative uses of GitHub as a platform for sharing non-code artifacts represent an important modification in the practice of open collaboration. We survey cases where GitHub has been used to facilitate collaboration on non-code outputs, identify its strengths and weaknesses when used in this mode, and propose conditions for successful collaborations on co-created text documents.